Heat setting machine with conveyor

ABSTRACT

A continuous heat set line for setting yarn, having spaced-apart, elongate, tubular entrance and exit cooling chambers interconnected by an elongate intermediate steam heat-setting chamber communicating therewith. The entrance and exit cooling chambers and the intermediate heat-setting chamber collectively define a single longitudinally-extending axis along the combined length thereof. Sealing heads seal the entrance and exit cooling chambers and the intermediate heat-setting chamber to a degree sufficient to maintain a pressurized condition within the heat-setting chamber. A yarn conveyor extends through the pretreatment chamber for conveying the yarn through the entrance and exit cooling chambers and the heat-setting chamber in a position substantially equidistant or very nearly equidistant from top and bottom walls. At least one piston and cylinder assembly moves sealing rolls into and out of position relative to each other, while independently-operating springs urge the rolls together sufficiently to effect a seal.

This application is a continuation of U.S. application Ser. No.11/548,522 filed on Oct. 11, 2006, which was a divisional of U.S.application Ser. No. 10/392,497, filed on Mar. 20, 2003.

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION

This invention relates to a machine and process for heat setting yarn,principally, but not exclusively, carpet yarn. The machine conditionstwisted yarns with saturated steam to increase the crystallinity of theyarn and lock the twist or the crimp into the yarn. The machine is acontinuous process machine with yarn entering one end of the machine,moving downstream through the machine and exiting the downstream endproperly treated and ready for the next production step which istypically winding onto yarn packages in preparation for carpet tufting.

In general, the heat setting machine includes a coiler or otheryarn-depositing device for depositing yarn on a moving conveyor whichcarries the yarn into a pretreatment chamber where the yarn is heated.The yarn then passes through a set of entrance sealing rolls whichmaintain a pressurized environment within the system. The yarn thenpasses into an entrance-cooling chamber where cool, dry air iscirculated through the yarn, cooling the yarn to a uniform temperatureand thus allowing redevelopment of the bulk in the yarn. This coolingchamber also protects the sealing rolls from the higher temperature ofthe heating chamber.

The yarn then passes into a heating chamber where a homogeneous mixtureof steam and air is circulated through the yarn. The yarn exits theheating chamber into an exit-cooling chamber where cool dry air iscirculated through the yarn to reduce the yarn temperature, removeexcess moisture, and protect a set of exit sealing rolls which cooperatewith the entrance sealing rolls to maintain a pressurized environmentwithin the system. The yarn then passes through the exit sealing rollsand can be further dried, separated and wound onto packages on a take-upwinder which runs in synchronization with the remaining components. Ayarn accumulator can be part of the system, allowing the system tocontinue operating during winder doffing cycles.

Several features are provided which differentiate the machine and methoddisclosed in this application from prior art machines. These featuresinclude a tunnel wherein two cooling chambers on either end of a heatingchamber communicate in alignment with each other along an axis extendingthe length of the combined cooling and heating chambers. There is nooffset from one zone to the other. This permits less expensivemanufacturing and a wider conveyor belt that can be positionedsubstantially equidistant from top and bottom walls of the chambers fortransporting the yarn through the system.

The novel system also includes an entrance and exit set of sealingrollers which maintain the pressure in the system. These sets of rollersare moved into and out of sealing position by a novel power-assistassembly such as pneumatic or hydraulic cylinders. The rollers arelocked into sealing with each other by a mechanical locking device thattakes the load off of the power-assist assembly and places the load ontoheavy springs which provide the resilience necessary to perform thesealing function while permitting the yarn to pass between the rollersinto and out of the heating chamber.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide a continuous heatset tunnel for setting yarn.

It is another object of the invention to provide a continuous heat setline that has a conveyor that extends generally along the lateralcenterline of the heat set tunnel to thereby provide for an increasedconveyor width.

It is another object of the invention to provide a continuous heat setline with sealing head rolls that are moved into and out of sealingposition by at least one piston and cylinder assembly.

It is another object of the invention to provide a continuous heat setline with sealing head rolls that are pressurized against each other bysprings operating independently of the piston and cylinder assembly.

These and other objects of the invention are achieved in the preferredembodiments disclosed below by providing a continuous heat set line forsetting yarn. The line includes spaced-apart, elongate, tubular entranceand exit cooling chambers interconnected by an elongate intermediatesteam heat-setting chamber communicating therewith. The entrance andexit cooling chambers and the intermediate heat-setting chambercollectively define a single longitudinally-extending axis along thecombined length thereof. A steam injector is included for injectingsteam at a predetermined pressure into the heat-setting chamber and ayarn conveyor extends through the entrance and exit cooling chambers andthe heat-setting chamber at a position equidistant from a top and bottomwall thereof for conveying the yarn therethrough. The line also includesa yarn depositing apparatus for depositing yarn in a uniform manner onthe yarn conveyor upstream of the entrance sealing means.

According to one preferred embodiment of the invention, the continuousheat set line further includes sealing means for sealing the entranceand exit cooling chambers and the intermediate heat-setting chamber to adegree sufficient to maintain a pressurized condition within theheat-setting chamber.

According to another preferred embodiment of the invention, the sealingmeans includes an entrance sealing roll apparatus positioned upstream ofthe entrance cooling chamber and an exit sealing roll apparatuspositioned downstream of the exit cooling chamber for sealing,respectively, the upstream end of the entrance cooling chamber and thedownstream end of the exit cooling chamber, each of the entrance andexit sealing roll apparatuses including a pair of sealing rollspositioned adjacent each other for allowing yarn on the conveyingapparatus to pass therebetween while preventing the escape ofpressurized steam from within the entrance and exit cooling chambers andthe intermediate steam heat-setting chamber.

According to another preferred embodiment of the invention, the sealingmeans includes a frame defining an opening through which the conveyorextends and a bottom sealing roll assembly carried by the frameincluding a rotatably-mounted bottom sealing roll positioned below theconveyor. The sealing means may also include a top sealing roll assemblycarried by the frame including a rotatably-mounted top sealing rollmounted in spaced-apart relation to the bottom sealing roll above theconveyor whereby the conveyor extends between the bottom sealing rolland the top sealing roll for carrying the yarn past the top and bottomsealing roll assemblies and into the entrance cooling chamber. At leastone piston and cylinder assembly can interconnect the frame and the topsealing roll assembly for moving the top sealing roll assembly betweenan opened position, and a closed position wherein the top roll restsagainst the bottom roll. Also, the sealing means may includepressurizing means for exerting sufficient pressure on the top roll toseal the top roll against the conveyor and the yarn carried thereon asthe conveyor is supported by the bottom roll.

According to another preferred embodiment of the invention, thepressurizing means of the sealing means includes springs carried by theframe for resiliently biasing the top roll against the yarn and conveyorwhen in its closed position.

According to another preferred embodiment of the invention, the sealingmeans includes lateral seals positioned to contact and seal againstradially-extending end walls of the top roll and the bottom roll.

According to another preferred embodiment of the invention, the yarndepositing apparatus comprises a yarn coiler for depositing uniform,overlapping coils of yarn on the yarn conveying apparatus.

According to another preferred embodiment of the invention, the yarnconveyor includes an endless fluid permeable conveyor belt extendingfrom the coiler to downstream of the exit cooling chamber.

According to another preferred embodiment of the invention, thecontinuous heat set line further includes a yarn packaging apparatus forremoving the yarn from the yarn depositing apparatus and forming theyarn into a package suitable for further downstream processing.

According to another preferred embodiment of the invention, thecontinuous heat set line includes a locking lever for urging a top rollinto contact with the conveyor.

According to another preferred embodiment of the invention, the lineincludes a locking pin for locking the locking lever into a positionwith the top roll urged into contact with the conveyor.

According to another preferred embodiment of the invention, the lineincludes a top lamella sealingly engaging a top roll along the lengththereof to prevent the escape of steam and pressure past the top rolland a bottom lamella sealingly engaging a bottom roll along the lengththereof to prevent the escape of steam and pressure past the bottomroll.

According to another preferred embodiment of the invention, a continuousheat set line for setting yarn includes spaced-apart, elongate, tubularentrance and exit cooling chambers interconnected by an elongateintermediate steam heat-setting chamber communicating therewith, theentrance and exit cooling chambers and the intermediate heat-settingchamber collectively defining a single longitudinally-extending axisalong the combined length thereof. The line also includes a steaminjector for injecting steam at a predetermined pressure into theheat-setting chamber and a steam pretreatment chamber positionedupstream of the entrance cooling chamber for applying a conditioningcharge of steam to the yarn before it enters the entrance coolingchamber. Also, the line includes a yarn conveyor extending through thepretreatment chamber, the entrance and exit cooling chambers and theheat-setting chamber at a position equidistant from a top and a bottomwall thereof for conveying the yarn therethrough and a yarn depositingapparatus for depositing yarn in a uniform manner on the yarn conveyorupstream of the pretreatment chamber.

According to another preferred embodiment of the invention, a method ofsetting yarn includes the step of providing a continuous heat set linefor setting yarn. The continuous heat set line includes spaced-apart,elongate, tubular entrance and exit cooling chambers interconnected byan elongate intermediate steam heat-setting chamber communicatingtherewith, the entrance and exit cooling chambers and the intermediateheat-setting chamber collectively defining a singlelongitudinally-extending axis along the combined length thereof. Theline also includes a steam injector for injecting steam at apredetermined pressure into the heat-setting chamber and a steampretreatment chamber positioned upstream of the entrance cooling chamberfor applying a conditioning charge of steam to the yarn before it entersthe entrance cooling chamber. The line further include a yarn conveyorextending through the entrance and exit cooling chambers and theheat-setting chamber at a position equidistant from top and bottom wallsthereof and a yarn depositing apparatus for depositing yarn in a uniformmanner on the yarn conveyor upstream of the pretreatment chamber. Themethod also includes conveying yarn through the continuous heat setline.

According to another preferred embodiment of the invention, the methodalso includes the step of sealing the entrance and exit cooling chambersand the intermediate heat-setting chamber to a degree sufficient tomaintain a pressurized condition within the heat-setting chamber.

According to another preferred embodiment of the invention, the methodalso includes the step of circulating cool, dry air through yarn in theentrance cooling chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects of the invention have been set forth above. Otherobjects and advantages of the invention will appear as the inventionproceeds when taken in conjunction with the following drawings, inwhich:

FIG. 1 is a vertical cross-section of a prior art heating tunnel;

FIG. 2A is a side elevation of a heat set tunnel according to thepresent invention;

FIG. 2B is a vertical cross-sectional view of a heat seat tunnelaccording to the invention;

FIG. 3 is a vertical cross section of a heating tunnel according to oneembodiment of the invention;

FIG. 4 is a vertical cross section of a heating tunnel according toanother embodiment of the invention including an external heatexchanger;

FIG. 5 is a vertical cross section of a heating tunnel according toanother embodiment of the invention including an external sump;

FIG. 6 is a vertical cross section of a heating tunnel according toanother embodiment of the invention including an external sump and anexterior heat exchanger;

FIG. 7 is a vertical cross-section of the exit and entrance coolingsections;

FIGS. 8 a-8 d shows four views of the of the entrance and exit sealinghead;

FIGS. 9 a is a perspective view of the sealing head in the closed,sealing position;

FIG. 9 b is a perspective view from the rear of the sealing head in theclosed, sealing position;

FIG. 9 c is perspective view from the rear of the sealing head in theclosed, sealing position, with parts removed for clarity;

FIG. 9 d is a top plan view of the sealing head;

FIG. 9 e is a side elevation of the sealing head in the closed, sealingposition; and

FIG. 9 f is a front elevation of the sealing head in the closed, sealingposition.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE

Referring now specifically to the drawings, a cross-section of a portionof a tubular heat set tunnel according to a prior art design isillustrated in FIG. 1 at reference numeral 1. The section represents theconfiguration of a central portion of the tunnel wherein the belt 2 is260 mm wide and resides 50 mm above the centerline of the tunnel section1. The belt 2 is positioned 100 mm above the waterline. Positioning thebelt above the centerline of the tunnel section 1 limits the width ofthe belt to a width less than would be possible at the centerlinediameter of the tunnel. This design, described in U.S. Pat. No.5,092,139, discloses positioning the central heating chamber with alongitudinally-extending axis which is disposed lower than the coolingchambers on either end, having the effect of moving the belt in the heatsetting tunnel closer to the longitudinally-extending axis of the heatsetting tunnel, but still above the centerline by approximately ⅙ to1/10 the diameter of the chamber. The '139 Patent teaches that thisarrangement is essential.

The invention according to the present invention is disclosed in FIGS.2-18, inclusive. As is shown in FIGS. 2A and 2B, the heat set tunnel 10according to the invention extends longitudinally along a supportingfloor surface and includes on one end an entrance sealing roll assembly20 and on the other end an exit sealing roll assembly 30. Downstream ofthe entrance sealing roll assembly 20 is an entrance cooling section 40connected by a cool/heat transition 41 to a steaming chamber 50comprised of tubular elongate entry, intermediate and exit heat settunnel segments 51, 52 and 53, respectively. A heat/cool transition 54interconnects the exit heat set tunnel segment 53 with an exit coolingsection 60.

The entrance cooling section 40 includes an exterior heat exchanger 42which takes heated yarn from a pre-treatment steaming chamber, notshown, and circulates cool, dry air through the yarn by means of a fan43, cooling the yarn to a uniform temperature and allowing bulk toredevelop in the yarn after passing under the rolls of the sealing rollassembly 20. See FIG. 7. The yarn then passes through the cool/heattransition 41 and into the entry heat set tunnel segment 51 where theyarn is heated again by live steam and heated air to a temperaturesufficient to set the bulk in the yarn. Air and steam is circulatedthrough the tunnel segments 51, 52 and 53 by an exterior recirculationconduit 55 and a fan 56.

The treated yarn passes through the heat/cool transition 54 into theexit cooling section which cools the yarn as it protects the rolls ofthe exit sealing roll assembly 30. The yarn is then conveyed to a winderwhere the yarn is packaged on suitable yarn packages and is ready forfurther processing.

The preferred embodiment of the heat set tunnel segment 51 is shown inFIG. 3, and is exemplary of tunnel segments 52 and 53. A sheet metaldrip shield 56 extends along the upper extent of the tunnel segment 51and encloses a conveyor belt 57 which extends the length of the heat settunnel 10. In the lower portion of the tunnel segment 51 are twolongitudinally-extending closed steam coils 58A and 58B which are usedto bring water in the lower portion of the tunnel 51 up to temperature.At this point these coils 58A and 58B are shut off and live steam isintroduced into the tunnel segment 51 through a perforated sparger 59.Note that the conveyor belt 57 extends very nearly along the diameter ofthe tunnel segment 51.

Another embodiment of a tunnel segment is shown in FIG. 4 at referencenumeral 80, and includes an elongate tubular enclosure 81 within whichis located a conveyor 82 within a sheet metal drip shield 83. Water inthe bottom of tunnel segment 80 is heated to temperature by acirculating external heat exchanger 84. A sparger 85 then supplies livesteam to the tubular enclosure 81.

Another embodiment of a tunnel segment is shown in FIG. 5 at referencenumeral 90, and includes an elongate tubular enclosure 91 within whichis located a conveyor 92 within a sheet metal drip shield 93. Water inthe bottom of tunnel segment 80 is heated to temperature in a sump 95 inwhich is contained two closed steam coils 96A, 96B and a sparger 97.After the water has been brought up to proper temperature, the sparger97 then supplies live steam to the tubular enclosure 91.

Another embodiment of a tunnel segment is shown in FIG. 6 at referencenumeral 100, and includes an elongate tubular enclosure 101 within whichis located a conveyor 102 within a sheet metal drip shield 103. Water inthe bottom of tunnel segment 80 is heated to temperature in a sump 105by means of an external heat exchanger 107. A sparger 97 then supplieslive steam to the tubular enclosure 91 to properly set the bulk in theyarn.

The entrance roll sealing assembly 20 is shown in FIGS. 8 a through 9 f.The exit roll sealing assembly 30 has the same construction. Theentrance roll sealing assembly 20 includes an entrance opening 120through which the conveyor 57 passes into the entrance cooling section40. A bottom sealing roll frame 121 mounts bottom drive gears 122A,122B, the shaft of which carries a bottom sealing roll 123 and hydrauliccylinder assemblies 124A, 124B. Piston rods 125A, 125B of the respectivehydraulic cylinder assemblies 124A, 124B are pivotally connected to thetop sealing roll frame 126. The top sealing roll frame 126 is pivotallymounted to the bottom sealing roll frame 121 by a pivot shaft 127. Thedistance and angle between the pivot of the piston rods 125A, 125B andthe pivot shaft 127 provides a lever arm which permits the top sealingroll frame 126 to be moved between a closed position, FIGS. 8 a, 8 b,and an open position, FIGS. 8 c, 8 d, by the actuation of the hydrauliccylinder assemblies 124A, 124B. While it is presently believed thathydraulic cylinders will best perform the function described above,pneumatic cylinders, worm gears, ball screw gears or other power assistmechanisms are also possible.

The top sealing roll frame 126 carries a top sealing roll 130, FIGS. 8b, 8 c which is rotated by driven gears 132A, 132B meshed with anddriven by drive gears 122A, 122B. The rolls 123 and 130 thus rotateagainst each other and provide a seal along their length, preventing theescape of pressure in the heating tunnel segments 51, 52, 53.

The sealing pressure against the rolls 123 and 130 necessary to preventthe escape of pressure is provided by opposed sets of heavy steelsprings 135, 136 mounted between the top sealing roll frame 126 and atop pressure plate 138. Adjustment screws 139 and 140 permit adjustmentof the springs to the correct pressure to seal the rolls 123 and 130against each other while not creating so much pressure that the rollbearings are damaged.

The hydraulic cylinders 124A, 124B serve only to raise and lower the topsealing roll frame 126 relative to the bottom sealing roll frame 121.When, for example, the top sealing roll frame 126 has been lowered ontothe bottom sealing roll frame 121 by the hydraulic cylinders 124A, 124B,pressure is applied to the rolls 123, 130 by means of a locking lever150 which is manually urged into a locking link assembly 151. See FIG. 9b. A locking cylinder 153 locks the locking lever 150 in its lockedposition, and a link pin 155 locks the locking link assembly 151 in itsdown, sealing and locked position.

As is best shown in FIG. 8 b, top and bottom lamellas 160, 161 are urgedagainst the front side of the top and bottom sealing rolls 130, 123,respectively, and seal against pressure escaping around the top of thetop roll 130 and the bottom roll 123. Similarly, side cylinders 163, 164urge side pressure plates 166, 167 against the opposed ends of thesealing rolls 123, 130 to prevent pressure leaks past the ends of therolls 123, 130, as shown in FIG. 9 d.

Yarn passing through the entrance sealing roll assembly 20 on theconveyor belt 57 is compressed as it passes between the top and bottomsealing rolls 130, 123 to the extent that pressure cannot escape pastthe compressed yarn. FIG. 9 e. Thus, the pressurized interior of theheat set tunnel 10 is effectively sealed at the entrance end from thesurrounding atmosphere.

The entire entrance sealing roll assembly 20 can be covered by aprotective shroud 170, as shown in FIGS. 13 and 9a.

As noted above, an identical exit roll sealing assembly 30 positioned inthe exit end of the heat set tunnel 10 performs the identical functionat the exit end, creating a closed environment for the heat setoperation.

A heat setting machine with a sealing head is described above. Variousdetails of the invention may be changed without departing from itsscope. Furthermore, the foregoing description of the preferredembodiment of the invention and the best mode for practicing theinvention are provided for the purpose of illustration only and not forthe purpose of limitation—the invention being defined by the claims.

1. A continuous heat set line for setting yarn, comprising: (a)spaced-apart, elongate, tubular entrance and exit cooling chambersinterconnected by an elongate intermediate steam heat-setting chambercommunicating therewith, the entrance and exit cooling chambers and theintermediate heat-setting chamber collectively defining a singlelongitudinally-extending axis along the combined length thereof; (b) asteam injector for injecting steam at a predetermined pressure into theheat-setting chamber; (c) a yarn conveyor extending through the entranceand exit cooling chambers and the heat-setting chamber at a positionequidistant from a top and bottom wall thereof for conveying the yarntherethrough; and (d) a yarn depositing apparatus for depositing yarn ina uniform manner on the yarn conveyor upstream of the entrance sealingmeans.
 2. A continuous heat set line for setting yarn according to claim1, further comprising sealing means for sealing the entrance and exitcooling chambers and the intermediate heat-setting chamber to a degreesufficient to maintain a pressurized condition within the heat-settingchamber.
 3. A continuous heat set line according to claim 1, wherein theyarn depositing apparatus comprises a yarn coiler for depositinguniform, overlapping coils of yarn on the yarn conveying apparatus.
 4. Acontinuous heat set line according to claim 1, wherein the yarn conveyorcomprises an endless fluid permeable conveyor belt extending from thecoiler to downstream of the exit cooling chamber.
 5. A continuous heatset line according to claim 1, and including a yarn packaging apparatusfor removing the yarn from the yarn depositing apparatus and forming theyarn into a package suitable for further downstream processing.
 6. Acontinuous heat set line according to claim 1, wherein the sealing meanscomprises an entrance sealing roll apparatus positioned upstream of theentrance cooling chamber and an exit sealing roll apparatus positioneddownstream of the exit cooling chamber for sealing, respectively, theupstream end of the entrance cooling chamber and the downstream end ofthe exit cooling chamber, each of the entrance and exit sealing rollapparatuses including a pair of sealing rolls positioned adjacent eachother for allowing yarn on the conveying apparatus to pass therebetweenwhile preventing the escape of pressurized steam from within theentrance and exit cooling chambers and the intermediate steamheat-setting chamber.
 7. A continuous heat set line according to claim2, wherein the sealing means comprises: (a) a frame defining an openingthrough which the conveyor extends; (b) a bottom sealing roll assemblycarried by the frame, including a rotatably-mounted bottom sealing rollpositioned below the conveyor; (c) a top sealing roll assembly carriedby the frame, and including a rotatably-mounted top sealing roll mountedin spaced-apart relation to the bottom sealing roll above the conveyorwhereby the conveyor extends between the bottom sealing roll and the topsealing roll for carrying the yarn past the top and bottom sealing rollassemblies and into the entrance cooling chamber; (d) at least onepiston and cylinder assembly interconnecting the frame and the topsealing roll assembly for moving the top sealing roll assembly betweenan opened position, and a closed position wherein the top roll restsagainst the bottom roll; and (e) pressurizing means for exertingsufficient pressure on the top roll to seal the top roll against theconveyor and the yarn carried thereon as the conveyor is supported bythe bottom roll.
 8. A continuous heat set line according to claim 7,wherein the pressurizing means comprises springs carried by the framefor resiliently biasing the top roll against the yarn and conveyor whenin its closed position.
 9. A continuous heat set line according to claim8, wherein the sealing means includes lateral seals positioned tocontact and seal against radially-extending end walls of the top rolland the bottom roll.
 10. A continuous heat set line according to claim1, further including a locking lever for urging a top roll into contactwith the conveyor.
 11. A continuous heat set line according to claim 10,further including a locking pin for locking the locking lever into aposition with the top roll urged into contact with the conveyor.
 12. Acontinuous heat set line according to claim 1, and including a toplamella sealingly engaging a top roll along the length thereof toprevent the escape of steam and pressure past the top roll and a bottomlamella sealingly engaging a bottom roll along the length thereof toprevent the escape of steam and pressure past the bottom roll.
 13. Acontinuous heat set line for setting yarn, comprising: (a) spaced-apart,elongate, tubular entrance and exit cooling chambers interconnected byan elongate intermediate steam heat-setting chamber communicatingtherewith, the entrance and exit cooling chambers and the intermediateheat-setting chamber collectively defining a singlelongitudinally-extending axis along the combined length thereof; (b) asteam injector for injecting steam at a predetermined pressure into theheat-setting chamber; (c) a steam pretreatment chamber positionedupstream of the entrance cooling chamber for applying a conditioningcharge of steam to the yarn before it enters the entrance coolingchamber; (d) a yarn conveyor extending through the pretreatment chamber,the entrance and exit cooling chambers and the heat-setting chamber at aposition equidistant from a top and a bottom wall thereof for conveyingthe yarn therethrough; and (e) a yarn depositing apparatus fordepositing yarn in a uniform manner on the yarn conveyor upstream of thepretreatment chamber.
 14. A method of setting yarn comprising the stepsof: (a) providing a continuous heat set line for setting yarn,comprising: (i) spaced-apart, elongate, tubular entrance and exitcooling chambers interconnected by an elongate intermediate steamheat-setting chamber communicating therewith, the entrance and exitcooling chambers and the intermediate heat-setting chamber collectivelydefining a single longitudinally-extending axis along the combinedlength thereof; (ii) a steam injector for injecting steam at apredetermined pressure into the heat-setting chamber; (iii) a steampretreatment chamber positioned upstream of the entrance cooling chamberfor applying a conditioning charge of steam to the yarn before it entersthe entrance cooling chamber; (iv) a yarn conveyor extending through theentrance and exit cooling chambers and the heat-setting chamber at aposition substantially equidistant from top and bottom walls thereof;and (v) a yarn depositing apparatus for depositing yarn in a uniformmanner on the yarn conveyor upstream of the pretreatment chamber; (b)conveying yarn through the continuous heat set line.
 15. The methodaccording to claim 14, further comprising the step of sealing theentrance and exit cooling chambers and the intermediate heat-settingchamber to a degree sufficient to maintain a pressurized conditionwithin the heat-setting chamber.
 16. The method according to claim 15,further comprising the step of circulating cool, dry air through yarn inthe entrance cooling chamber.